1. Field of the Invention
This invention relates in general to the field of marking instruments, including crayons and pencils, and, in particular, to marking compositions for use in the manufacture of such instruments. More particularly, the invention relates to marking compositions which are washable from fabrics and surfaces.
2. Brief Description of the Prior Art
There are disclosed in the prior art a number of washable crayons, including the washable waxy crayon disclosed in U.S. Pat. No. 3,993,492. That patent discloses that an acceptable washable marking composition may be made by including a mixture of three specific polyethylene glycol materials having specified molecular weight ranges; namely, a first component of a medium molecular weight (2,000-4,500) polyethylene glycol, a second component of a high molecular weight (6,000-7,500) polyethylene glycol, and a third component of a low molecular weight (400-800) polyethylene glycol.
Many such crayons have reasonably good washability, but they are deficient not only in their physical properties but also in their marking characteristics. A truly acceptable washable crayon, like any other crayon, must, at a minimum, resist breakage, have minimal flaking, be easy to apply, and have a clean color. It is in these respects that washable crayons developed to date have been deficient.